Nonvolatile semiconductor storage device and manufacturing method thereof

Abstract

A charge holding insulating film in a memory cell is constituted by a laminated film composed of a bottom insulating film, a charge storage film, and a top insulating film on a semiconductor substrate. Further, by performing a plasma nitriding treatment to the bottom insulating film, a nitride region whose nitrogen concentration has a peak value and is 1 atom % or more is formed on the upper surface side in the bottom insulating film. The thickness of the nitride region is set to 0.5 nm or more and 1.5 nm or less, and the peak value of nitrogen concentration is set to 5 atom % or more and 40 atom % or less, and a position of the peak value of nitrogen concentration is set within 2 nm from the upper surface of the bottom insulating film, thereby suppressing an interaction between the bottom insulating film and the charge storage film.

1. A nonvolatile semiconductor storage device having a semiconductor substrate and a memory cell, the memory cell comprising:
 a first insulating film formed on the semiconductor substrate; 
 a charge storage film formed on the first insulating film; 
 a second insulating film formed on the charge storage film; and 
 a gate electrode formed on the second insulating film, 
 wherein a nitride region whose nitrogen concentration has a peak value and is 1 atom % or more is formed on a charge storage film side in the first insulating film, and a thickness of the nitride region is 0.5 nm or more and 1.5 nm or less. 
 
     
     
       2. The nonvolatile semiconductor storage device according to  claim 1 ,
 wherein the peak value of nitrogen concentration in the first insulating film is 5 atom % or more and 40 atom % or less. 
 
     
     
       3. The nonvolatile semiconductor storage device according to  claim 1 ,
 wherein the peak value of nitrogen concentration in the first insulating film is located in an area within 2 nm from an interface between the first insulating film and the charge storage film. 
 
     
     
       4. The nonvolatile semiconductor storage device according to  claim 1 ,
 wherein physical thickness of the charge storage film is 20 nm or less. 
 
     
     
       5. The nonvolatile semiconductor storage device according to  claim 1 ,
 wherein the first insulating film is a silicon oxide film or a silicon oxynitride film. 
 
     
     
       6. The nonvolatile semiconductor storage device according to  claim 1 ,
 wherein the second insulating film is a silicon oxide film. 
 
     
     
       7. The nonvolatile semiconductor storage device according to  claim 1 ,
 wherein physical thickness of the first insulating film is 2.5 nm or more and 6 nm or less, and physical thickness of the second insulating film is 4 nm or more and 6 nm or less. 
 
     
     
       8. The nonvolatile semiconductor storage device according to  claim 1 ,
 wherein the charge storage film is a hafnium oxide film. 
 
     
     
       9. The nonvolatile semiconductor storage device according to  claim 1 ,
 wherein a nitride region whose nitrogen concentration has a peak value and is 1 atom % or more is formed on a second insulating film side in the charge storage film. 
 
     
     
       10. The nonvolatile semiconductor storage device according to  claim 9 ,
 wherein the peak value of nitrogen concentration in the charge storage film is 5 atom % or more and 40 atom % or less.